In an air bag device for an occupant in a passenger seat, a casing (sometimes referred to as a container) accommodates an air bag and an inflator therein and has a lid to cover an opening of the casing. The lid is sometimes referred to as a cover door or a deployment door. The inflator acts to deploy the air bag in the event of a collision so that the lid is pushed by the deploying air bag and then opens toward the cabin of the vehicle. As a result, the air bag is deployed widely to the vehicle cabin.
The lid is designed to be provided with tear lines so that the lid is torn along the tear lines, to make a flap therein which opens toward the vehicle cabin.
With reference to FIGS. 10 through 12, the description will now be made with regard to a structure of a conventional air bag device and the operation thererof for an occupant in the passenger seat, which has such a lid with tear lines. FIG. 11 is a sectional view taken along a line XI--XI in FIG. 10, and FIG. 12 is a view for explaining the operation thereof. In the air bag device 10, an air bag 14 in its folded state is accommodated in a casing 12. The casing 12 is provided with an inflator 16 for deploying the air bag 14. The casing 12 has an opening in the front side or the upper side thereof to face toward the vehicle cabin. A lid 18 is arranged to cover the opening of the casing 12. The lid 18 has a structure comprising a main body 18a made of synthetic resin and a metallic reinforcing plate 18b provided inside (or in a rear portion of) the main body 18a. A numeral 20 designates an opening in an instrument panel 22 for mounting the air bag device.
The lid 18 is provided with a first tear line 28 and second tear lines 24, 26. The second tear line 24 extends along a left side of the vehicle body and the second tear line 26 extends along a right side of the vehicle body. The first tear line 28 extends so that one end of the second tear line 24 and one end of the second tear line 26 are connected to each other via the first tear line 28.
In order to attach the lid 18 to the casing 12, the lid is provided with mounting pieces 32, 34 projecting therefrom. The mounting pieces 32, 34 are fixed to the casing 12 by rivets or bolts 36, 38, respectively.
As the vehicle mounted with the air bag 10 comes into collision, the inflator 16 acts to deploy the air bag 14 and the air bag 14 then pushes the lid 18. Therefore, the lid 18 is torn along the tear lines 24, 26, and 28, with the result that a flap 30 surrounded by the tear lines 24, 26, and 28 opens like a door as shown in FIG. 12. Therefore, the air bag 14 deploys widely in the vehicle cabin.
Though the tear lines 24, 26, and 28 are disposed to form a C-shape in FIGS. 10 through 12, tear lines 24a, 26a, and 28a of a lid 18' may be disposed to form a H-shape as shown in FIG. 13. In this case, a flap 32 of the lid 18' opens upwardly as shown by an arrow A, and a flap 34 of the lid 18' opens downwardly as shown by an arrow B. A numeral 22a designates an instrument panel.
Such tear lines may be formed by cutting grooves continuously along a line to be torn or in a dotted line like a seam. It should be noted that some grooves may be deeply formed at intervals. In case where the cover has a double-layered structure with a hard layer and a soft layer, a slit may be formed in the hard layer along a line to be torn.
As mentioned above, in the conventional air bag device, a tear begins to travel along the first tear line 28 or 28a and subsequently travels along the second tear lines 24 and 26 or 24a and 26a due to the spread of the tear so that the lid opens widely.
The first tear line 28 or 28a and the second tear lines 24 and 26 or 24a and 26a intersect substantially at a right angle in connecting corners therebetween. Therefore, there is a possibility that the tear traveling along the first tear lines 28 or 28a also travels substantially straight in the lid toward the Sides of the vehicle body by inertia.